1. Field of the Invention
The present invention relates to a two-dimensional CCD (charge-coupled device) image sensor.
2. Description of the Related Art
Conventional two-dimensional CCD image sensors comprise a plurality of vertical transfer channels arranged to receive charge packets from a matrix array of photodiodes, a plurality of row electrodes connected to the vertical transfer channels for shifting the charge packets row by row along the vertical transfer channels, and a horizontal transfer channel arranged to receive charge packets from the vertical transfer channels. The horizontal transfer channel is formed with a plurality of patterns of doped adjoining regions. Each pattern has a first and a second set of a storage region and two barrier regions. Groups of electrodes are successively arranged on the horizontal transfer channel. Each of the groups has first, second, third and fourth electrodes, and each of the electrodes partially overlaps adjacent electrodes with an insulation layer interposed therebetween. For shifting charge packets along the horizontal transfer channel, the first and second electrodes are connected in pair and the third and fourth electrodes are connected in pair, and the respective electrode pairs are driven by clock voltage pulses of opposite phases. The first and third electrodes of each group respectively overlie the storage regions of the first and second sets, the second electrode of the group overlies the barrier regions of the first set and partially overlaps the final row electrode with an insulating layer interposed therebetween, and the fourth electrode of the group overlies the barrier regions of the second set. In the prior art horizontal transfer channel, the storage region of the first set and one of the barrier regions of the first set are connected to a corresponding vertical transfer channel to receive charge packets therefrom.
However, when CCD image sensors were connected to respective video monitors, few vertical black streaks appeared on some of the monitor screens. The image sensors were considered to be the cause of the failure. Since the failure rate of the image sensors is substantial, there exists a need for eliminating the vertical black streaks.